Local ground effects in near-field and far-field areas on seismically protected buildings

This paper presents a 2-D numerical study on the nonlinear seismic response of buildings equipped with two types of energy dissipators, which dissipate energy activating two different mechanisms. Three types of reinforced concrete buildings with 3, 7 and 15 stories, respectively representative of short, medium and long period ranges, are considered. Dissipators are placed on steel diagonal braces at all the floors; their sliding threshold (or yielding) forces are taken as 100% of those generated by the equivalent static lateral forces recommended by EC8 for a ductile moment resisting frame. The input consists of six recorded earthquakes, 3 representatives of near-field earthquakes and 3 representatives of far-field earthquakes. Each input is considered once from the bedrock and once filtered by a common ground with several layers of different thicknesses. The responses of the buildings are discussed and compared emphasizing the filtering effects produced by the ground.     

Global SMOS Soil Moisture Retrievals from The Land Parameter Retrieval Model

A recent study by Van der Schalie et al. (2015) showed good results for applying the Land Parameter Retrieval Model (LPRM) on SMOS observations over southeast Australia and optimizing and evaluating the retrieved soil moisture (θ in m³ m⁻³) against ground measurements from the OzNet sites. In this study, the LPRM parameterization is globally updated for SMOS against modelled θ from MERRA-Land (MERRA) and ERA-Interim/Land (ERA) over the period of July 2010–December 2010, mainly focusing on two parameters: the single scattering albedo (ω) and the roughness (h). The Pearson's coefficient of correlation (r) increased rapidly when increasing the ω up to 0.12 and reached a steady state from thereon, no significant spatial pattern was found in the estimation of the single scattering albedo, which could be an artifact of the used parameter estimation procedure, and a single value of 0.12 was therefore used globally. The h was defined as a function of θ and varied slightly for the different angle bins, with maximum values of 1.1–1.3 as the angle changes from 42.5° to 57.5°.This resulted in an average r of 0.51 and 0.47, with a bias (m³ m⁻³) of −0.02 and −0.01 and an unbiased root mean square error (ubrmse in m³ m⁻³) of 0.054 and 0.056 against MERRA (ascending and descending). For ERA this resulted in an r of 0.61 and 0.53, with a bias of −0.03 and an ubrmse 0.055 and 0.059. The resulting parameterization was then used to run LPRM on SMOS observations over the period of July 2010–December 2013 and evaluated against SMOS Level 3 (L3) θ and available in situ measurements from the International Soil Moisture Network (ISMN). The comparison with L3 shows that the LPRM θ retrievals are very similar, with for the ascending set very high r of over 0.9 in large parts of the globe, with an overall average of 0.85 and the descending set performing less with an average of 0.74, mainly due to the negative r over the Sahara. The mean bias is 0.03, with an ubrmse of 0.038 and 0.044. In this study there are three major areas where the LPRM retrievals do not perform well: very dry sandy areas, densely forested areas and over high latitudes, which are all known limitations of LPRM. The comparison against in situ measurement from the ISMN give very similar results, with average r for LPRM of 0.65 and 0.61 (0.64 and 0.59 for L3) for the ascending and descending sets, while having a comparable bias and ubrmse over the different networks. This shows that LPRM used on SMOS observations produce θ retrievals with a similar quality as the SMOS L3 product.     

GEO和MEO卫星联合被动定位系统的建模与仿真

在双星主动式卫星定位系统的基础上,对建设GEO卫星和MEO卫星联合被动定位系统进行了探讨。介绍了一种联合被动定位系统的基本结构,建立了定位解算模型并进行了定位误差分析。通过编制相应的仿真软件对所提出的定位系统方案进行了仿真,验证了在我国分步建设被动式全球导航卫星系统的技术可行性。     

被动微波遥感反演中国西部地区雪深、雪水当量算法初步研究

雪深、雪水当量是积雪研究中重要参数，其在流域水量平衡和融雪径流预报以及雪灾监测与评价中起着重要作用。Chang等(1987)以辐射传输理论和米氏散射为理论基础，假定积雪密度和颗粒大小为常数，利用实测雪深数据和SMMR的亮温数据，通过统计回归方法，建立了雪深与18 GHz和37 GHz水平极化的亮温梯度之间的关系，发展了SMMR半经验的反演雪深的算法。后在此基础上又发展了针对SSM/I的半经验反演雪深算法。2002年发射的装载于Aqua卫星上的AMSR E是新一代的被动微波辐射计，性能较以往星载被动微波辐射计有较大提高，采用了改进后的SSM/I的半经验算法作为其估算全球雪水当量的反演算法。 将AMSR E的雪水当量产品与气象台站观测的雪水当量进行比较，发现在新疆地区和青藏高原地区雪水当量的RMSE分别达到31.8 mm和21 mm。本研究旨在建立基于AMSR E亮温数据，适用于中国西部地区的雪深和雪水当量反演算法。首先收集整理了2003年新疆地区的雪深、雪水当量数据和AMSR E亮温数据，去除错误样本，利用统计回归的方法，建立了新疆的反演雪深、雪水当量的半经验算法，算法中加入积雪覆盖度参数，较以往的算法有所改进，与气象台站观测数据比较，结果也表明新疆地区建立的经验算法较AMSR E的雪水当量算法有较大改进，RMSE为15.7 mm。但青藏高原地区因海拔高，地形复杂，大部分地区积雪较浅,空间分布不均和冻土存在等诸多因素运用同样的方法建立反演算法，结果不甚理想，以后的研究将重点消除这些干扰因素。     

Evolution of the passive continental margins of India—a geophysical appraisal

The passive continental margins of India have evolved as India broke and drifted away from East Antarctica, Madagascar and Seychelles at various geological times. In this study, we have attempted to collate and re-examine gravity and topographic/bathymetry data over India and the adjoining oceans to understand the structure and tectonic evolution of these margins, including processes such as crustal/lithosphere extension, subsidence due to sedimentation, magmatic underplating and so on. The Eastern Continental Margin of India (ECMI) seems to have evolved in a complex rift and shear tectonic settings in its northern and southern segments, respectively, and bears similarities with its conjugate in East Antarctica. Crustal extension rates are uniform along the stretch of the ECMI in spite of the presence or absence of crustal underplated material, variability in lithospheric strength and tectonic style of evolution ranging from rifting to shearing. The Krishna-Godavari basin is underlain by a strong ( 30 km) elastic lithosphere, while the Cauvery basin is underlain by a thin elastic lithosphere ( 3 km). The coupling between the ocean and continent lithosphere along the rifted segment of the ECMI is across a stretched continental crust, while it is direct beneath the Cauvery basin. The Western Continental Margin of India (WCMI) seems to have developed in an oblique rift setting with a strike-slip component. Unlike the ECMI, the WCMI is in striking contrast with its conjugate in the eastern margin of Madagascar in respect of sedimentation processes and alignment of magnetic lineations and fracture zones. The break up between eastern India and East Antarctica seems to have been accommodated along a Proterozoic mobile belt, while that between western India and Madagascar is along a combination of both mobile belt and cratonic blocks.     

基于简化参数方法的蒙古干旱区土壤湿度被动微波遥感

卫星被动微波遥感土壤湿度,是准确分析大空间尺度上陆表水分变化信息的有效手段.美国航天局(NASA)发布的基于AMSR-E观测亮温资料的全球土壤湿度反演产品,在蒙古干旱区的实际精度并不令人满意.本文基于对地表微波辐射传输中地表粗糙度和植被层影响的简化处理方法,采用AMSR-E的6.9 GHz,10.7 GHz和18.7 GHz之V极化亮温资料,应用多频率反演算法,并以国际能量和水循环协同观测计划(The Coordinated Energy and Water Cycle Observations Project)即CEOP实验在蒙古国东部荒漠地区的地面实验资料作为先验知识,获取被动微波遥感模型的优化参数,以期获得蒙古干旱区精度更高的土壤湿度遥感估算结果.分析表明,本文方法反演的白天和夜间土壤湿度结果与地面验证值之间的均方根误差(RMSE)接近0.030 cm³/cm³, 证明所用方法在不需要其他辅助资料或参数帮助下,可较精确地反演干旱区表层土壤湿度信息,能够全天候、动态监测大空间尺度的土壤湿度变化,可为干旱区气候变化研究及陆面过程模拟和数据同化研究提供高精度的表层土壤湿度初始场资料.     

噪声层析成像在壳幔结构研究中的现状与展望

噪声层析成像是一门最近发展起来的新技术, 用环境噪声为数据研究地球结构, 摆脱了对震源信号的依赖。 由于噪声资料含有丰富的短周期信息, 噪声层析成像技术的应用, 大大提高了对地壳浅层结构的分辨能力, 并可有效用于城市地下结构的研究。 本文通过对噪声成像的发展现状、 计算方法和研究进展等几个方面的综述, 分析了噪声层析成像的优缺点, 对噪声层析成像技术的发展方向进行了展望。 噪声资料结合地震面波和体波反演的各向异性研究, 有助于更准确地揭示壳幔结构和深部动力特征。 综合运用噪声分析技术与其它有源信号的分析技术, 将会促进对壳幔地震学参数动态变化和地震前后的物性变化的研究探索。     

Assessing the potential of passive seismic receiver functions for ore body exploration

We use a passive seismic high-frequency receiver function method to image the shallow structure around a mine site. This is a relatively new application of a standard method for mapping major discontinuities in the crust and upper mantle at a scale small enough to be relevant in an exploration context. Data collected in a 21-instrument array is inverted for isotropic velocity structure. The retrieved velocities in the south-eastern part of the array match very well with available sonic log measurements in the top 800 m. Based on the differences in receiver function behaviour for stations across the array, recovered velocity profiles and their similarity to sonic log measurements, the target area is split into two separate regions along a north-northeast trending line that correlates well to the strike of the dominant structure in the area – the Navan Fault. Our results demonstrate the ability of receiver functions to provide both qualitative and quantitative information in an exploration environment.     

Integrated biomarker assessment of the effects exerted by treated produced water from an onshore natural gas processing plant in the North Sea on the mussel Mytilus edulis

The biological impact of a treated produced water (PW) was investigated under controlled laboratory conditions in the blue mussel, Mytilus edulis. Mussel health status was assessed using an integrated biomarker approach in combination with chemical analysis of both water (with SPMDs), and mussel tissues. Acyl-CoA oxidase activity, neutral lipid accumulation, catalase activity, micronuclei formation, lysosomal membrane stability in digestive cells and haemocytes, cell-type composition in digestive gland epithelium, and the integrity of the digestive gland tissue were measured after 5 week exposure to 0%, 0.01%, 0.1%, 0.5% and 1% PW. The suite of biomarkers employed were sensitive to treated PW exposure with significant sublethal responses found at 0.01-0.5% PW, even though individual chemical compounds of PW were at extremely low concentrations in both water and mussel tissues. The study highlights the benefits of an integrated biomarker approach for determining the potential effects of exposure to complex mixtures at low concentrations. Biomarkers were integrated in the Integrative Biological Response (IBR/n) index.